1. Field of the Invention
The present invention relates to an apparatus for controlling a flow rate of a gas supplied when processing a processing target, for example, a semiconductor wafer, and a processing apparatus using the flow rate controller.
2. Description of the Related Art
In general, a semiconductor device is manufactured by repeatedly performing various processes, such as film forming, etching, annealing, and oxidization diffusing, on a semiconductor wafer, for example, a silicon substrate. In order to perform the above-described various processes, various processing gases are used. In this case, there is a need to control a process temperature, a process pressure, and a flow rate of the processing gas with high accuracy in order to stably perform the process.
A flow rate controller, for example, a mass flow controller, is generally used as an apparatus for controlling the flow rate of the processing gas with high accuracy (refer to Patent References 1 and 2). The flow rate controller obtains a flow rate (mass flow rate) by using amount of heat movement, which occurs due to flow of a gas inside a sensor pipe, as a resistance variation of a resistance wire having a resistance value varying depending on a temperature. In this case, conversion data showing a relationship between a flow rate instruction signal, which corresponds to a flow rate setting value input by an operator, and a target flow rate is previously stored in the flow rate controller. The flow rate controller automatically controls a flow rate under a feedback control so as to realize the target flow rate corresponding to the flow rate instruction signal.
However, since the flow rate controller controls the flow rate based on the amount of heat movement occurring due to flow of a gas, if a used gaseous species has a different specific heat, the flow rate of the gas changes due to the different specific heat. Thus, in a conventional flow rate controller, a correction value, that is, a conversion factor (hereinafter, referred to as “CF value”), of various gaseous species is previously determined based on a reference gaseous species, for example, N2 gas. Also, when the flow rate controller is supplied, the flow rate controller in which conversion data obtained based on the CF value of a gaseous species designated when a user ordered is stored is supplied.
In an actual processing apparatus, various gases are used. In this case, one flow rate controller may control a flow rate of one or more gaseous species in addition to a gaseous species determined when the flow rate controller is supplied, in order to reduce an installation cost. In this case, an operator of the processing apparatus manually calculates a corrected flow rate based on the CF value of a gaseous species of which a flow rate is to be newly controlled, and the corrected flow rate is input by the operator so as to store the corrected flow rate.
However, since a CF value differs depending on a manufacturer or model of a flow rate controller, a calculation becomes complicated when inputting the CF value, and also, a calculation error may occur.
3. Prior Art Reference
(Patent Reference 1) Japanese Laid-Open Patent Publication No. 2005-222173
(Patent Reference 2) International Patent Publication No. WO 2008-016189